1. Field of the Invention
The present invention relates to a neutral controller for an automobile automatic transmission, and a method thereof. More particularly, the present invention relates to the neutral controller that initiate the neutral control after a predetermined period beginning when the neutral control initiation conditions are satisfied, and the method thereof.
2. Description of Prior Art
A neutral controller and a method thereof for an automobile automatic transmission are disclosed by Tokko No. Sho 63-33024, Tokko No. Sho 63-35869 and Tokko No. Sho 63-33585. The prior art is more specifically a neutral controller that automatically puts an automatic transmission into a neutral position when the accelerator is OFF, that is, the throttle is closed and the vehicle is stopped. In the prior art, an engine load and fuel consumption rate may be reduced by automatically putting a gear in a neutral position when the gear select lever is in the D (drive) position, the throttle valve is closed, and the vehicle is stopped.
For a general automatic transmission, application of the brake is added to the above-listed conditions to permit the vehicle to move during idling (so-called creeping). Then, the automatic transmission is put in the neutral position only when the brake is applied. Therefore, the conditions that cause the automatic transmission to initiate the neutral position (neutral control) include the gear select lever is in the D position, the throttle is closed completely, the vehicle is stopped, and the brake is applied.
It is generally known to program the neutral control so that it does not start for a predetermined delay time after all the conditions are satisfied. This is because it must be confirmed that the conditions are satisfied, and the automobile is not just in a temporary operation. This assumes the neutral control is not unintentionally initiated.
The neutral control is cancelled when any one of the above conditions is not satisfied, so that the operator may promptly accelerate the vehicle as he or she wishes. As mentioned above, the neutral control is initiated after the delay time beginning when the initiation conditions are satisfied, and is cancelled when any one condition is not satisfied. Thus, the vehicle may be operated according to the operator's intention.
In the prior art, it improves fuel efficiency to shorten the delay time as much as possible, that is, initiate the neutral control as soon as possible. Regarding real efficiency, the operator does not feel any inconsistency with a short delay time when he stops the vehicle at the traffic light and starts the vehicle again in his normal running conditions. This is because the vehicle stays still for a rather long time while waiting for the traffic light.
However, when slow running and stopping is alternately repeated, such as in a case of a traffic jam, the neutral control is initiated and cancelled during the stop. Under these conditions, the operator notices the vehicle's diminished driving characteristics because a transmitted torque change (a shift shock analogue) is often caused at the cancellation of the neutral control. The transmitted torque change is also often caused when the operator repeatedly operates the vehicle by creeping and brake pumping, such as when parking in a garage.
Even after the neutral control is initiated, such as when waiting for a stop traffic light to change, the neutral control may be cancelled when the operator unintentionally releases the brake. The neutral control is resumed when the operator applies the brake again, causing transmitted torque change. It is possible to avoid these by lengthening the delay time before the neutral control initiation. However, that diminishes the improving effect on the fuel efficiency. In the prior art, the improvement of fuel efficiency and the improvement of driving characteristics in the traffic congestion are mutually exclusive.